In U.S. Pat. Nos. 3,330,429; 3,825,135; 4,063,658 and 4,122,961 there are disclosed various forms of heavy duty carriers intended to pick up, transport and dump large ladles or slag pots of the kind used in foundries, steel mills and other metal and slag generating industries. The larger ones of such pots and ladles, when loaded, often weigh on the order of 200 to 400 tons. Slag pots are typically made of very heavy-walled rugged construction and can take considerable knocking, pounding, dropping and other abuse in normal handling operations. Ladles for transporting molten metal, on the other hand, are usually made with relatively thin-walled metal shells lined with refractory material which is quite fragile in nature and can be easily damaged if the ladle is bumped or jarred while being picked up, carried or set down.
Generally speaking, the carriers disclosed in the above patents include a trailer with a pair of heavy trailing arms on which the load supporting wheels are mounted and a generally U-shaped rigid cradle pivotally mounted on the trailer arms for embracing the pot or ladle and supporting it through large laterally spaced hooks suspended from the cradle side arms to engage the pot or ladle trunnions. The suspension hooks are usually spaced just wide enough apart to clear the sides of the pot or ladle when the trailer is backed into the lift position, thus requiring very accurate maneuvering of the large, heavy trailer lest the pot or ladle be unnecessarily bumped or jarred. Likewise, the trailer must be very carefully steered and positioned to place the pot or ladle in the proper location or stand before it is lowered onto its support.